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Mike T. · 09-29-2021, 08:52 AM

The middle of the LCD on my HP22S has started to darken and now shows as a grey eclipse. I'm guessing this not recoverable? The contrast controls make no difference.

It still works but it is a bit harder to read the display than it should be so it isn't really suitable for everyday use anymore. Otherwise the machine in in good shape.

Massimo Gnerucci · (This post was last modified: 09-29-2021 09:28 AM by Massimo Gnerucci.)

(09-29-2021 08:52 AM)Mike T. Wrote: The middle of the LCD on my HP22S has started to darken and now shows as a grey eclipse. I'm guessing this not recoverable? The contrast controls make no difference.

It still works but it is a bit harder to read the display than it should be so it isn't really suitable for everyday use anymore. Otherwise the machine in in good shape.

Have a look here and here.

Mike T. · 09-29-2021, 11:01 PM

(09-29-2021 09:25 AM)Massimo Gnerucci Wrote:
(09-29-2021 08:52 AM)Mike T. Wrote: The middle of the LCD on my HP22S has started to darken and now shows as a grey eclipse. I'm guessing this not recoverable? The contrast controls make no difference.

It still works but it is a bit harder to read the display than it should be so it isn't really suitable for everyday use anymore. Otherwise the machine in in good shape.

Have a look here and here.

Thank you,

I'm very happy to find it is reversible!

Looks a bit tricky for someone as clumsy as me though.

isanchez · (This post was last modified: 10-01-2021 10:32 AM by isanchez.)

Hi,

i see I am refered here to a procedure I posted in the past.

Just to add something very important to it (despite I did not experienced, but received some feedback from others).

It seems that there are two layers in the inner side of the display: the mentioned silvered one you have to peel off, as this is the source of the dark eliptical stain; and another transparent one, below, difficult to see, that HAS NOT TO BE REMOVED, as it provides some kind of relective properties to the LCD display. If this layer is removed, the contrast of the display is lost.

As I said, this comes from other colleagues experience, so take it into account and do not be so agressive removing/cleaning the inner side of the display.

Good luck and kind regards.

Ignacio

ettlz · (This post was last modified: 10-09-2021 01:30 PM by ettlz.)

I just got a 20S with reflector burn (made in Brazil -- a good deal at the price I paid, given how rare the HP 2xSs seem to be in the UK). My experience was:

Using a 3.2mm drill to cut out the four heat-stakes under the battery cover left me sufficient material on the back cover to install small self-tapping screws on reassembly, as the friction pins in the corners are terrible for breaking off.
The display's reflective layer, which is the outer rear layer with the white backing, was attached with what appears to be clear acetoxy silicone -- i.e., bathroom sealant. It stank of vinegar. It took a good bit of isopropanol, cotton buds, isopropanol-impregnated wipes and elbow grease to get rid of all the residue. But this is a different 7-segment LCD so may have different layers to the 7x5 matrix display in the 22S.
Working with aluminium foil (even the thick variety) to fashion a substitute reflector was a pain and I gave up on this. I wasn't able to come up with a method that both kept the foil even and would prevent possible shorts.
In the end I cut out a piece of white card and put that in place with no adhesive. The result is a slightly darker display, but it is still quite legible. Later on I might try with some silvered craft card.

Geoff Quickfall · 10-09-2021, 03:30 PM

For backing, I have a roll of silver (semigloss) Christmas parcel wrapping paper.

cruff · 10-09-2021, 03:31 PM

(10-01-2021 10:31 AM)isanchez Wrote: It seems that there are two layers in the inner side of the display: the mentioned silvered one you have to peel off, as this is the source of the dark eliptical stain; and another transparent one, below, difficult to see, that HAS NOT TO BE REMOVED, as it provides some kind of relective properties to the LCD display. If this layer is removed, the contrast of the display is lost.

That transparent layer is a polarizing filter, and as you say if it comes off the contrast will not be good. You could probably obtain some polarizing film to replace it.

Geoff Quickfall · (This post was last modified: 10-09-2021 05:32 PM by Geoff Quickfall.)

I do this a lot with older Seiko digital watches.

One layer is a polarizer. The polarizing lines decompose due to UV light over time. After removing the outer sheet of polarized film take your new sheet of polarized film. Rotate above the lcd panel while it is on until you get the best contrast. Mark the orientation, cut to size keeping the high contrast orientation and place over the lcd.

In retrospect, Joe Horn did a presentation on the polarizing orientation and their inconsistencies in orientation at HHC2008 HHC 2008 photos.

Wearing a polarized sunglass will cause you to orient the calculator display so that you can read it!

Cheers, Geoff

2008 was my first HHC meeting.

ettlz · 10-14-2021, 08:20 PM

So I tried using a more reflective, silvered card behind my 20S's screen. It brightened it up, but it now might be a bit too reflective Big Grin

(Yes, that is my phone.)

[Image: o9XXGAc.jpg]

Mike T. · 10-16-2021, 08:53 PM

I'm a bit reluctant to try opening up my HP22S but given the responses here it looks like it isn't too difficult, does anyone have any photos showing the process (and probably more importantly how to close it up again afterwards!)

Thanks

vaklaff · 10-17-2021, 10:33 AM

(10-14-2021 08:20 PM)ettlz Wrote: So I tried using a more reflective, silvered card behind my 20S's screen. It brightened it up, but it now might be a bit too reflective (Yes, that is my phone.)

Actually I like it very much, you gave the little machine quite a personality, congrats!

ijabbott · 10-17-2021, 12:58 PM

(10-16-2021 08:53 PM)Mike T. Wrote: I'm a bit reluctant to try opening up my HP22S but given the responses here it looks like it isn't too difficult, does anyone have any photos showing the process (and probably more importantly how to close it up again afterwards!)

Thanks

Here are a couple of videos by Logan West (for keyboard connector repairs, rather than display backing replacement). Be careful not to bend the bezel like he did on one of the videos. It does not look like he drilled the tops of the heat staked rivets off before prying it apart.

Only one video per post allowed, so here is a link to the other one:
https://youtu.be/Uo4EZG0NQbc